Multipoint nanostructure-film touch screen

ABSTRACT

A touch screen comprising at least one nanostructure film and capable of detecting multiple touches occurring at the same time at distinct locations in a plane of the touch screen is described. The touch screen may comprise a sensing layer, a driving layer and/or a shielding layer. At least one of these layers may comprise a nanostructure film, and at least two of these layers may be formed on a common substrate.

This application claims priority to U.S. Provisional Application No.60/976,235, filed Sep. 28, 2007 and entitled “MULTIPOINTNANOSTRUCTURE-FILM TOUCH SCREEN,” the entire contents of which arehereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to an electronic device having atouch screen comprising at least one nanostructure film. Moreparticularly, the present invention relates to a nanotube-film touchscreen capable of sensing multiple points at the same time.

BACKGROUND OF THE INVENTION

Many modern and/or emerging applications require at least one deviceelectrode that has not only high electrical conductivity, but highoptical transparency as well. Such applications include, but are notlimited to, touch screens (e.g., analog, resistive, 4-wire resistive,5-wire resistive, surface capacitive, projected capacitive, multi-touch,etc.), displays (e.g., flexible, rigid, electro-phoretic,electro-luminescent, electrochromatic, liquid crystal (LCD), plasma(PDP), organic light emitting diode (OLED), etc.), solar cells (e.g.,silicon (amorphous, protocrystalline, nanocrystalline), cadmiumtelluride (CdTe), copper indium gallium selenide (CIGS), copper indiumselenide (CIS), gallium arsenide (GaAs), light absorbing dyes, quantumdots, organic semiconductors (e.g., polymers, small-moleculecompounds)), solid state lighting, fiber-optic communications (e.g.,electro-optic and opto-electric modulators) and microfluidics (e.g.,electrowetting on dielectric (EWOD)).

As used herein, a layer of material or a sequence of several layers ofdifferent materials is said to be “transparent” when the layer or layerspermit at least 50% of the ambient electromagnetic radiation in relevantwavelengths to be transmitted through the layer or layers. Similarly,layers which permit some but less than 50% transmission of ambientelectromagnetic radiation in relevant wavelengths are said to be“semi-transparent.”

Currently, the most common transparent electrodes are transparentconducting oxides (TCOs), specifically indium-tin-oxide (ITO) on glass.However, ITO can be an inadequate solution for many of theabove-mentioned applications (e.g., due to its relatively brittlenature, correspondingly inferior flexibility and abrasion resistance),and the indium component of ITO is rapidly becoming a scarce commodity.Additionally, ITO deposition usually requires expensive,high-temperature sputtering, which can be incompatible with many deviceprocess flows. Hence, more robust, abundant and easily-depositedtransparent conductor materials are being explored.

Touch screens are display overlays which may be pressure sensitive(resistive), electrically-sensitive (capacitive), acoustically-sensitive(surface acoustic wave (SAW)) and/or photo-sensitive (infra-red). Theeffect of such overlays is to allow a display to be used as an inputdevice, with such displays often attached to computers and/or networks.Touch screens typically include a touch panel, a controller and asoftware driver. The touch panel is a transparent panel with atouch-sensitive surface, which registers touch events and sends thesesignals to the controller. The controller processes these signals andsends the data to the computers and/or networks, wherein the softwaredriver translates the touch events into computer events.

One problem found in conventional touch screen technologies is that manyare only capable of reporting a single point even when multiple objectsare placed on the sensing surface. That is, they lack the ability totrack multiple points of contact simultaneously. In resistive andcapacitive technologies, an average of all simultaneously occurringtouch points are determined and a single point which falls somewherebetween the touch points is reported. In surface wave and infraredtechnologies, it is difficult, if not impossible, to discern the exactposition of multiple touch points that fall on the same horizontal orvertical lines due to masking. In either case, faulty results aregenerated.

A related problem found in many conventional touch screen technologiesis that they utilize transparent conductive materials that areill-suited for touch panel functionality. For example, ITO can be aninadequate touch panel solution, given that ITO is relatively brittleand consequently prone to mechanical degradation, in which case faultyresults are generated. Additionally, currently-available ITO depositionmethods can be limiting in terms of the possible touch screen devicearchitectures enabled thereby.

SUMMARY OF THE INVENTION

The present invention describes nanostructure films. Nanostructures haveattracted a great deal of recent attention due to their exceptionalmaterial properties. Nanostructures may include, but are not limited to,nanotubes (e.g., single-walled carbon nanotubes (SWNTs), multi-walledcarbon nanotubes (MWNTs), double-walled carbon nanotubes (DWNTs),few-walled carbon nanotubes (FWNTs)), other fullerenes (e.g.,buckyballs), graphene flakes/sheets, and/or nanowires (e.g., metallic(e.g., Ag, Ni, Pt, Au), semiconducting (e.g., InP, Si, GaN), dielectric(e.g., SiO₂, TiO₂), organic, inorganic). Nanostructure films maycomprise at least one interconnected network of such nanostructures, andmay similarly exhibit exceptional material properties. For example,nanostructure films comprising at least one interconnected network ofsubstantially carbon nanotubes (e.g., wherein nanostructure density isabove a percolation threshold) can exhibit extraordinary strength andelectrical conductivity, as well as efficient heat conduction andsubstantial optical transparency. As used herein, “substantially” shallmean that at least 40% of components are of a given type.

In one embodiment, the invention relates to a nanostructure-film touchscreen comprising at least one nanostructure-film electrode configuredto detect multiple touches or near touches that occur at the same timeand at distinct locations in the plane of the touch panel, and toproduce distinct signals representative of the location of the toucheson the plane of the touch panel for each of the multiple touches.Nanostructure films according to embodiments of the present inventioninclude, but are not limited to, those comprising networks of nanotubes,nanowires, nanoparticles and/or graphene flakes. Such nanostructurefilms can be transparent, conductive, and substantially moremechanically robust than ITO.

In one embodiment, the nanostructure-film touch screen comprises atleast two nanostructure films (e.g., at least two of a sensing layer, adriving layer and a shielding layer) are formed on a common substrate.Said nanostructure films may be formed on the same side of the commonsubstrate, or on opposite sides of the substrate. Such nanostructurefilms may be electrically separated by a dielectric layer (e.g., thecommon substrate, a dielectric layer coated over a nanostructure film,etc.).

In one embodiment, the invention relates to a display arrangementwherein the touch screen is a substantially transparent panel that ispositioned in front of a screen for displaying a graphical userinterface, such that the screen can be viewed through the panel.

In one embodiment, the invention relates to a computer system comprisinga processor operatively coupled to the display arrangement, andconfigured to execute instructions and carry out operations associatedwith the computer system.

In one embodiment, the invention relates to a computer-implementedmethod, comprising receiving multiple touches on the surface of ananostructure-film touch screen at the same time, separately recognizingeach of the multiple touches and reporting touch data based on therecognized multiple touches.

In one embodiment, the invention relates to a touch screen methodcomprising driving a plurality of sensing points, reading the outputsfrom all the sensing lines connected to the sensing points, producingand analyzing an image of a nanostructure-film touch screen plane at onemoment in time in order to determine where objects are touching thenanostructure-film touch screen. The method additionally includescomparing the current image to a past image in order to determine achange at the objects touching the touch screen.

In one embodiment, the invention relates to a digital signal processingmethod, comprising receiving raw data that includes values for eachtransparent capacitive sensing node of a nanostructure-film touchscreen, filtering the raw data, generating gradient data, calculatingthe boundaries for touch regions base on the gradient data, andcalculating the coordinates for each touch region.

Other features and advantages of the invention will be apparent from theaccompanying drawings and from the detailed description. One or more ofthe above-disclosed embodiments, in addition to certain alternatives,are provided in further detail below with reference to the attachedfigures. The invention is not limited to any particular embodimentdisclosed; the present invention may be employed in not only transparentconductive film applications, but in other nanostructure applications aswell (e.g., nontransparent electrodes, transistors, diodes, conductivecomposites, electrostatic shielding, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is better understood from reading the following detaileddescription of the preferred embodiments, with reference to theaccompanying figures in which:

FIG. 1 is a scanning electron microscope (SEM) image of a nanostructurefilm according to one embodiment of the present invention;

FIG. 2 is a perspective view of a display arrangement, in accordancewith one embodiment of the present invention;

FIG. 3 shows an image of the nanostructure-film touch screen plane at aparticular point in time, in accordance with one embodiment of thepresent invention;

FIG. 4 is a multipoint touch method, in accordance with one embodimentof the present invention;

FIG. 5 is a block diagram of a computer system, in accordance with oneembodiment of the present invention;

FIG. 6 is a partial top view of a transparent multiple pointnanostructure-film touch screen, in accordance with one embodiment ofthe present invention;

FIG. 7 is a partial top view of a transparent multi pointnanostructure-film touch screen, in accordance with one embodiment ofthe present invention;

FIG. 8 is a front elevation view, in cross section of a displayarrangement, in accordance with one embodiment of the present invention;

FIG. 9 is a top view of a transparent multipoint nanostructure-filmtouch screen, in accordance with another embodiment of the presentinvention;

FIG. 10 is a partial front elevation view, in cross section of a displayarrangement, in accordance with one embodiment of the present invention;

FIGS. 11A and 11B are partial top view diagrams of a driving layer and asensing layer, in accordance with one embodiment;

FIG. 12 is a simplified diagram of a mutual capacitance circuit, inaccordance with one embodiment of the present invention;

FIG. 13 is a diagram of a charge amplifier, in accordance with oneembodiment of the present invention;

FIG. 14 is a block diagram of a capacitive sensing circuit, inaccordance with one embodiment of the present invention;

FIG. 15 is a flow diagram, in accordance with one embodiment of thepresent invention;

FIG. 16 is a flow diagram of a digital signal processing method, inaccordance with one embodiment of the present invention;

FIGS. 17A-E show touch data at several steps, in accordance with oneembodiment of the present invention;

FIG. 18 is a side elevation view of an electronic device, in accordancewith one embodiments of the present invention;

FIG. 19 is a side elevation view of an electronic device, in accordancewith one embodiment of the present invention; and

FIG. 20 is a partial front elevation view, in cross section of a displayarrangement, in accordance with one embodiment of the present invention.

Features, elements, and aspects of the invention that are referenced bythe same numerals in different figures represent the same, equivalent,or similar features, elements, or aspects in accordance with one or moreembodiments of the system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, a nanostructure film according to one embodiment ofthe present invention comprises at least one interconnected network ofsingle-walled carbon nanotubes (SWNTs). Such film may additionally oralternatively comprise other nanotubes (e.g., MWNTs, DWNTs), otherfullerenes (e.g., buckyballs), graphene flakes/sheets, and/or nanowires(e.g., metallic (e.g., Ag, Ni, Pt, Au), semiconducting (e.g., InP, Si,GaN), dielectric (e.g., SiO₂, TiO₂), organic, inorganic).

Such nanostructure film may further comprise at least onefunctionalization material bonded to the nanostructure film. Forexample, a dopant bonded to the nanostructure film may increases theelectrical conductivity of the film by increasing carrier concentration.Such dopant may comprise at least one of Iodine (I₂), Bromine (Br₂),polymer-supported Bromine (Br₂), Antimonypentafluride (SbF₅),Phosphoruspentachloride (PCl₅), Vanadiumoxytrifluride (VOF₃), Silver(II)Fluoride (AgF₂), 2,1,3-Benzoxadiazole-5-carboxylic acid,2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole,2,5-Bis-(4-aminophenyl)-1,3,4-oxadiazole,2-(4-Bromophenyl)-5-phenyl-1,3,4-oxadiazole,4-Chloro-7-chlorosulfonyl-2,1,3-benzoxadiazole,2,5-Diphenyl-1,3,4-oxadiazole,5-(4-Methoxyphenyl)-1,3,4-oxadiazole-2-thiol,5-(4-Methylphenyl)-1,3,4-oxadiazole-2-thiol,5-Phenyl-1,3,4-oxadiazole-2-thiol,5-(4-Pyridyl)-1,3,4-oxadiazole-2-thiol, Methyl viologen dichloridehydrate, Fullerene-C60, N-Methylfulleropyrrolidine,N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine, Triethylamine (TEA),Triethanolanime (TEA)-OH, Trioctylamine, Triphenylphosphine,Trioctylphosphine, Triethylphosphine, Trinapthylphosphine,Tetradimethylaminoethene, Tris(diethylamino)phosphine, Pentacene,Tetracene,N,N′-Di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl)-4,4′-diaminesublimed grade, 4-(Diphenylamino)benzaldehyde, Di-p-tolylamine,3-Methyldiphenylamine, Triphenylamine,Tris[4-(diethylamino)phenyl]amine, Tri-p-tolylamine, Acradine Orangebase, 3,8-Diamino-6-phenylphenanthridine, 4-(Diphenylamino)benzaldehydediphenylhydrazone, Poly(9-vinylcarbazole), Poly(1-vinylnaphthalene),Poly(2-vinylpyridine)n-oxide, Triphenylphosphine,4-Carboxybutyl)triphenylphosphonium bromide, Tetrabutylammoniumbenzoate, Tetrabutylammonium hydroxide 30-hydrate, Tetrabutylammoniumtriiodide, Tetrabutylammonium bis-trifluoromethanesulfonimidate,Tetraethylammonium trifluoromethanesulfonate, Oleum (H₂SO₄—SO₃), Triflicacid and/or Magic Acid.

Such dopant may be bonded covalently or noncovalently to the film.Moreover, the dopant may be bonded directly to the film or indirectlythrough and/or in conjunction with another molecule, such as astabilizer that reduces desorption of dopant from the film. Thestabilizer may be a relatively weak reducer (electron donor) or oxidizer(electron acceptor), where the dopant is a relatively strong reducer(electron donor) or oxidizer (electron acceptor) (i.e., the dopant has agreater doping potential than the stabilizer). Additionally oralternatively, the stabilizer and dopant may comprise a Lewis base andLewis acid, respectively, or a Lewis acid and Lewis base, respectively.Exemplary stabilizers include, but are not limited to, aromatic amines,other aromatic compounds, other amines, imines, trizenes, boranes, otherboron-containing compounds and polymers of the preceding compounds.Specifically, poly(4-vinylpyridine) and/or tri-phenyl amine havedisplayed substantial stabilizing behavior in accelerated atmospherictesting (e.g., 1000 hours at 65° C. and 90% relative humidity).

Stabilization of a dopant bonded to a nanostructure film may also oralternatively be enhanced through use of an encapsulant. The stabilityof a non-functionalized or otherwise functionalized nanostructure filmmay also be enhanced through use of an encapsulant. Accordingly, yetanother embodiment of the present invention comprises a nanostructurefilm coated with at least one encapsulation layer. This encapsulationlayer preferably provides increased stability and environmental (e.g.,heat, humidity and/or atmospheric gases) resistance. Multipleencapsulation layers (e.g., having different compositions) may beadvantageous in tailoring encapsulant properties. Exemplary encapsulantscomprise at least one of a fluoropolymer, acrylic, silane, polyimideand/or polyester encapsulant (e.g., PVDF (Hylar CN, Solvay), Teflon AF,Polyvinyl fluoride (PVF), Polychlorotrifluoroethylene (PCTFE),Polyvinylalkyl vinyl ether, Fluoropolymer dispersion from Dupont (TE7224), Melamine/Acrylic blends, conformal acrylic coating dispersion,etc.). Encapsulants may additionally or alternatively comprise UV and/orheat cross-linkable polymers (e.g., Poly(4-vinyl-phenol)).

Electronic performance of a nanostructure film according to oneembodiment may additionally or alternatively be enhanced by bondingmetal (e.g., gold, silver) nanoparticles to nanotubes (e.g., usingelectro and/or electroless plating). Such bonding may be performedbefore, during and/or after the nanotubes have formed an interconnectednetwork.

A nanostructure film according to one embodiment may additionally oralternatively comprise application-specific additives. For example, thinnanotube films can be inherently transparent to infrared radiation, thusit may be advantageous to add an infrared (IR) absorber thereto tochange this material property (e.g., for window shielding applications).Exemplary IR absorbers include, but are not limited to, at least one ofa cyanine, quinone, metal complex, and photochronic. Similarly, UVabsorbers may be employed to limit the nanostructure film's level ofdirect UV exposure.

A nanostructure film according to one embodiment may be fabricated usingsolution-based processes. In such processes, nanostructures may beinitially dispersed in a solution with a solvent and dispersion agent.Exemplary solvents include, but are not limited to, deionized (DI)water, alcohols and/or benzo-solvents (e.g., tolulene, xylene).Exemplary dispersion agents include, but are not limited to, surfactantsand biopolymers (e.g., carboxymethylcellulose (CMC)). Applicablesurfactants may be non-ionic (e.g., Triton-X, alcohols,N,N-Dimethyl-N-[3-(sulfooxy)propyl]-1-nonanaminium hydroxide inner salt,N,N-Dimethyl-N-[3-(sulfooxy)propyl]-1-decanaminium hydroxide inner salt,Glycocholic acid hydrate, Chenodeoxycholic acid diacetate methyl ester,N-Nonanoyl-N-methylglucamine, Tetrabutylammonium nitrate,3-(Decyldimethylammonio)-propane-sulfonate inner salt,3-(N,N-Dimethyloctylammonio)propanesulfonate inner salt, EMPIGEN® BBdetergent, 1-Dodecyl-2-pyrrolidinone), cationic (e.g., thonzoniumbromide, cetyl trimethylammonium bromide (CTAB), benzyltrimethylammoniumbromide (BTAB), behentrimonium chloride (BTAC), dodecyltrimethylammoniumchloride surfactant (DTAC)), anionic (e.g., sodium dodecyl sulfate(SDS), sodium 1-decanesulfonate, sodium 1-dodecanesulfonate, sodiumdodecylbenzenesulfonate (SDBS), sodium 1-heptanesulfonate) orZwitterionic (e.g., Dodecyl betaine, Dodecyl dimethylamine oxide,Cocamidopropyl betaine, Coco ampho glycinate). It may be advantageous toemploy a multiple-surfactant system, for example, mixtures of cationicand anionic surfactants or mixtures of nonionic and anionic surfactants.Dispersion may be further aided by mechanical agitation, such as bycavitation (e.g., using probe and/or bath sonicators), shear (e.g.,using a high-shear mixer and/or rotor-stator), impingement (e.g.,rotor-stator) and/or homogenization (e.g., using a homogenizer). Coatingaids may also be employed in the solution to attain desired coatingparameters, e.g., wetting and adhesion to a given substrate;additionally or alternatively, coating aids may be applied to thesubstrate. Exemplary coating aids include, but are not limited to,aerosol OT, fluorinated surfactants (e.g., Zonyl FS300, FS500, FS62A),alcohols (e.g., hexanol, heptanol, octanol, nonanol, decanol, undecanol,dodecanol, saponin, ethanol, propanol, butanol and/or pentanol),aliphatic amines (e.g., primary, secondary (e.g., dodecylamine),tertiary (e.g., triethanolamine), quartinary), TX-100, FT248, TergitolTMN-10, Olin 10G and/or APG325.

The resulting dispersion may be coated onto a substrate using a varietyof coating methods. Coating may entail a single or multiple passes,depending on the dispersion properties, substrate properties and/ordesired nanostructure film properties. Exemplary coating methodsinclude, but are not limited to, spray-coating, dip-coating,drop-coating and/or casting, roll-coating, transfer-stamping, slot-diecoating, curtain coating, [micro]gravure printing, flexoprinting and/orinkjet printing. Exemplary substrates may be flexible or rigid, andinclude, but are not limited to, glass, elastomers (e.g., saturatedrubbers, unsaturated rubbers, thermoplastic elastomers (TPE),thermoplastic vulcanizates (TPV), polyurethane rubber, polysulfiderubber, resilin and/or elastin) and/or plastics (e.g., polymethylmethacrylate (PMMA), polyolefin(s), polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polycarbonate (PC), polyethersulfone(PES) and/or Arton). Flexible substrates may be advantageous in havingcompatibility with roll-to-roll (a.k.a. reel-to-reel) processing,wherein one roll supports uncoated substrate while another roll supportscoated substrate. As compared to a batch process, which handles only onecomponent at a time, a roll-to-roll process represents a dramaticdeviation from current manufacturing practices, and can reduce capitalequipment and product costs, while significantly increasing throughput.Nanostructure films may be printed first on a flexible substrate, e.g.,to take advantage of roll-to-roll capabilities, and subsequentlytransferred to a rigid substrate (e.g., where the flexible substratecomprises a release liner, laminate and/or other donor substrate oradhesion layer (e.g., A-187, AZ28, XAMA, PVP, CX-100, PU)). Substrate(s)may be pre-treated to improve adhesion of the nanotubes thereto (e.g.,by first coating an adhesion layer/promoter onto the substrate).

Once coated onto a substrate, the dispersion may be heated to removesolvent therefrom, such that a nanostructure film is formed on thesubstrate. Exemplary heating devices include a hot plate, heating rod,heating coil and/or oven. The resulting film may be washed (e.g., withwater, ethanol and/or IPA) and/or oxidized (e.g., baked and/or rinsedwith an oxidizer such as nitric acid, sulfuric acid and/or hydrochloricacid) to remove residual dispersion agent and/or coating aid therefrom.

Dopant, other additives and/or encapsulant may further be added to thefilm. Such materials may be applied to the nanostructures in the filmbefore, during and/or after film formation, and may, depending on thespecific material, be applied in gas, solid and/or liquid phase (e.g.,gas phase NO₂ or liquid phase nitric acid (HNO₃) dopants). Suchmaterials may moreover be applied through controlled techniques, such asthe coating techniques enumerated above in the case of liquid phasematerials (e.g., slot-die coating a polymer encapsulant).

A nanostructure film according to one embodiment may be patterned before(e.g., using lift-off methods, pattern-pretreated substrate), during(e.g., patterned transfer printing, screen printing (e.g., usingacid-paste as an etchant, with a subsequent water-wash), inkjetprinting) and/or after (e.g., using laser ablation or masking/etchingtechniques) fabrication on a substrate. Patterning may be effected bynot only selective removal or coating of nanostructures, butadditionally or alternatively by changing the material properties of thefilm (e.g., selectively rendering nanotubes non-conductive by exposingsuch nanotubes to electromagnetic radiation).

In one exemplary embodiment, an optically transparent and electricallyconductive nanostructure film comprising an interconnected network ofSWNTs was fabricated on a transparent and flexible plastic substrate viaa multi-step spray and wash process. A SWNT dispersion was initiallyformulated by dissolving commercially-available SWNT powder (e.g., P3from Carbon Solutions) in DI water with 1% SDS, and probe sonicated for30 minutes at 300 W power. The resulting dispersion was then centrifugedat 10k rcf (relative centrifugal field) for 1 hour, to remove largeagglomerations of SWNTs and impurities (e.g., amorphous carbon and/orresidual catalyst particles). In parallel, a PC substrate was immersedin a silane solution (a coating aid comprising 1% weight of3-aminopropyltriethoxysilane in DI water) for approximately fiveminutes, followed by rinsing with DI water and blow drying withnitrogen. The resulting pre-treated PC substrate (Tekra 0.03″ thick withhard coating) was then spray-coated over a 100° C. hot plate with thepreviously-prepared SWNT dispersion, immersed in DI water for 1 minute,then sprayed again, and immersed in DI water again. This process ofspraying and immersing in water may be repeated multiple times until adesired sheet resistance (e.g., film thickness) is achieved.

In a related exemplary embodiment, a doped nanostructure film comprisingan interconnected network of SWNTs was fabricated on a transparent andflexible substrate using the methods described in the previous example,but with a SWNT dispersion additionally containing a TCNQF₄ dopant. Inanother related embodiment, this doped nanostructure film wassubsequently encapsulated by spin-coating a layer of parylene thereonand baking.

In another exemplary embodiment, a SWNT dispersion was first prepared bydissolving SWNT powder (e.g., P3 from Carbon Solutions) in DI water with1% SDS and bath-sonicated for 16 hours at 100 W, then centrifuged at15000 rcf for 30 minutes such that only the top ¾ portion of thecentrifuged dispersion is selected for further processing. The resultingdispersion was then vacuum filtered through an alumina filter with apore size of 0.1-0.2 μm (Watman Inc.), such that an opticallytransparent and electrically conductive SWNT film is formed on thefilter. DI water was subsequently vacuum filtered through the film forseveral minutes to remove SDS. The resulting film was then transferredto a PET substrate by a PDMS (poly-dimethylsiloxane) based transferprinting technique, wherein a patterned PDMS stamp is first placed inconformal contact with the film on the filter such that a patterned filmis transferred from the filter to the stamp, and then placed inconformal contact with the PET substrate and heated to 80° C. such thatthe patterned film is transferred to the PET. In a related exemplaryembodiment, this patterned film may be subsequently doped via immersionin a gaseous NO₂ chamber. In another related exemplary embodiment, thefilm may be encapsulated by a layer of PMPV, which, in the case of adoped film, can reduce desorption of dopant from the film.

In yet another exemplary embodiment, an optically transparent,electrically conductive, doped and encapsulated nanostructure filmcomprising an interconnected network of FWNTs was fabricated on atransparent and flexible substrate. CVD-grown FWNTs (OE grade fromUnidym, Inc.) were first dissolved in DI water with 0.5% Triton-X, andprobe sonicated for one hour at 300 W power. The resulting dispersionwas then slot-die coated onto a PET substrate, and baked at about 100°C. to evaporate the solvent. The Triton-X was subsequently removed fromthe resulting FWNT film by immersing the film for about 15-20 seconds innitric acid (10 molar). Nitric acid may be effective as both anoxidizing agent for surfactant removal, and a doping agent as well,improving the sheet resistance of the film from 498 ohms/sq to about 131ohms/sq at about 75% transparency, and 920 ohms/sq to about 230 ohms/sqat 80% transparency in exemplary films. In related exemplaryembodiments, these films were subsequently coated with triphenylaminewhich stabilized the dopant (i.e., the film exhibited a less than 10%change in conductivity after 1000 hours under accelerated agingconditions (65° C.)). In other related exemplary embodiments, the filmswere then encapsulated with Teflon AF.

In another exemplary embodiment, FWNT powder was initially dispersed inwater with SDS (e.g., 1%) surfactant by sonication (e.g., bathsonication for 30 minutes, followed by probe sonication for 30 minutes);1-dodecanol (e.g., 0.4%) was subsequently added to the dispersion bysonication (e.g., probe sonication for 5 minutes) as a coating aid, andthe resulting dispersion was Meyer rod coated onto a PEN substrate. SDSwas then removed by rinsing the film with DI water, and the 1-dodecanolwas removed by rinsing with ethanol. This resulting opticallytransparent and electrically conductive films passed anindustry-standard “tape test,” (i.e., the FWNT film remained on thesubstrate when a piece of Scotch tape was pressed onto and then peeledoff of the film); such adhesion between the FWNT film and PEN was notachieved with SDS dispersions absent use of a coating aid.

In one embodiment nanostructure films (e.g., as described above) may beincorporated into device as transparent electrodes.

FIG. 2 is a perspective view of a display arrangement 30, in accordancewith one embodiment of the present invention. The display arrangement 30includes a display 34 and a transparent nanostructure-film touch screen36 positioned in front of the display 34. The display 34 is configuredto display a graphical user interface (GUI) including perhaps a pointeror cursor as well as other information to the user. The transparentnanostructure-film touch screen 36, on the other hand, is an inputdevice that is sensitive to a user's touch, allowing a user to interactwith the graphical user interface on the display 34. By way of example,the nanostructure-film touch screen 36 may allow a user to move an inputpointer or make selections on the graphical user interface by simplypointing at the GUI on the display 34.

In general, nanostructure-film touch screens 36 recognize a touch eventon the surface 38 of the nanostructure-film touch screen 36 andthereafter output this information to a host device. The host device mayfor example correspond to a computer such as a desktop, laptop, handheldor tablet computer. The host device interprets the touch event andthereafter performs an action based on the touch event. Conventionally,touch screens have only been capable of recognizing a single touch eventeven when the touch screen is touched at multiple points at the sametime (e.g., averaging, masking, etc.). Unlike conventional touchscreens, however, the nanostructure-film touch screen 36 shown herein isconfigured to recognize multiple touch events that occur at differentlocations on the touch sensitive surface 38 of the nanostructure-filmtouch screen 36 at the same time. That is, the nanostructure-film touchscreen 36 allows for multiple contact points T1-T4 to be trackedsimultaneously, i.e., if four objects are touching thenanostructure-film touch screen, then the nanostructure-film touchscreen tracks all four objects. As shown, the nanostructure-film touchscreen 36 generates separate tracking signals S1-S4 for each touch pointT1-T4 that occurs on the surface of the nanostructure-film touch screen36 at the same time. The number of recognizable touches may be about 15.15 touch points allows for all 10 fingers, two palms and 3 others.

The multiple touch events can be used separately or together to performsingular or multiple actions in the host device. When used separately, afirst touch event may be used to perform a first action while a secondtouch event may be used to perform a second action that is differentthan the first action. The actions may for example include moving anobject such as a cursor or pointer, scrolling or panning, adjustingcontrol settings, opening a file or document, viewing a menu, making aselection, executing instructions, operating a peripheral deviceconnected to the host device etc. When used together, first and secondtouch events may be used for performing one particular action. Theparticular action may for example include logging onto a computer or acomputer network, permitting authorized individuals access to restrictedareas of the computer or computer network, loading a user profileassociated with a user's preferred arrangement of the computer desktop,permitting access to web content, launching a particular program,encrypting or decoding a message, and/or the like.

Recognizing multiple touch events is generally accomplished with amultipoint sensing arrangement. The multipoint sensing arrangement iscapable of simultaneously detecting and monitoring touches and themagnitude of those touches at distinct points across the touch sensitivesurface 38 of the nanostructure-film touch screen 36. The multipointsensing arrangement generally provides a plurality of transparent sensorcoordinates or nodes 42 that work independent of one another and thatrepresent different points on the nanostructure-film nanostructure-filmtouch screen 36. When plural objects are pressed against thenanostructure-film touch screen 36, one or more sensor coordinates areactivated for each touch point as for example touch points T1-T4. Thesensor coordinates 42 associated with each touch point T1-T4 produce thetracking signals S1-S4.

In one embodiment, the nanostructure-film touch screen 36 includes aplurality of capacitance sensing nodes 42. The capacitive sensing nodesmay be widely varied. For example, the capacitive sensing nodes may bebased on self capacitance or mutual capacitance. In self capacitance,the “self” capacitance of a single electrode is measured as for examplerelative to ground. In mutual capacitance, the mutual capcitance betweenat least first and second electrodes is measured. In either case, eachof the nodes 42 works independent of the other nodes 42 so as to producesimultaneously occurring signals representative of different points onthe nanostructure-film touch screen 36.

In order to produce a transparent nanostructure-film touch screen 36,the capacitance sensing nodes 42 are formed with a transparentconductive medium comprising at least one nanostructure film. In selfcapacitance sensing arrangements, the transparent conductive medium ispatterned into spatially separated electrodes and traces. Each of theelectrodes represents a different coordinate and the traces connect theelectrodes to a capacitive sensing circuit. The coordinates may beassociated with Cartesian coordinate system (x and y), Polar coordinatesystem (r, .theta.) or some other coordinate system. In a Cartesiancoordinate system, the electrodes may be positioned in columns and rowsso as to form a grid array with each electrode representing a differentx, y coordinate. During operation, the capacitive sensing circuitmonitors changes in capacitance that occur at each of the electrodes.The positions where changes occur and the magnitude of those changes areused to help recognize the multiple touch events. A change incapacitance typically occurs at an electrode when a user places anobject such as a finger in close proximity to the electrode, i.e., theobject steals charge thereby affecting the capacitance.

In mutual capacitance, the transparent conductive medium is patternedinto a group of spatially separated lines formed on two differentlayers. Driving lines are formed on a first layer and sensing lines areformed on a second layer. Although separated by being on differentlayers, the sensing lines traverse, intersect or cut across the drivinglines thereby forming a capacitive coupling node. The manner in whichthe sensing lines cut across the driving lines generally depends on thecoordinate system used. For example, in a Cartesian coordinate system,the sensing lines are perpendicular to the driving lines thereby formingnodes with distinct x and y coordinates. Alternatively, in a polarcoordinate system, the sensing lines may be concentric circles and thedriving lines may be radially extending lines (or vice versa). Thedriving lines are connected to a voltage source and the sensing linesare connected to capacitive sensing circuit. During operation, a currentis driven through one driving line at a time, and because of capacitivecoupling, the current is carried through to the sensing lines at each ofthe nodes (e.g., intersection points). Furthermore, the sensing circuitmonitors changes in capacitance that occurs at each of the nodes. Thepositions where changes occur and the magnitude of those changes areused to help recognize the multiple touch events. A change incapacitance typically occurs at a capacitive coupling node when a userplaces an object such as a finger in close proximity to the capacitivecoupling node, i.e., the object steals charge thereby affecting thecapacitance.

By way of example, the signals generated at the nodes 42 of thenanostructure-film touch screen 36 may be used to produce an image ofthe touch screen plane at a particular point in time. Referring to FIG.3, each object in contact with a touch sensitive surface 38 of thenanostructure-film touch screen 36 produces a contact patch area 44.Each of the contact patch areas 44 covers several nodes 42. The coverednodes 42 detect surface contact while the remaining nodes 42 do notdetect surface contact. As a result, a pixilated image of the touchscreen plane can be formed. The signals for each contact patch area 44may be grouped together to form individual images representative of thecontact patch area 44. The image of each contact patch area 44 mayinclude high and low points based on the pressure at each point. Theshape of the image as well as the high and low points within the imagemay be used to differentiate contact patch areas 44 that are in closeproximity to one another. Furthermore, the current image, and moreparticularly the image of each contact patch area 44 can be compared toprevious images to determine what action to perform in a host device.

Nanostructure films according to the embodiments of the presentinvention may be patterned by methods including, but not limited to,laser etching, dry etching, stamping and/or liftoff. Patterning methodsaccording to one embodiment of the present invention are specificallytuned for etching nanostructure films.

For example, solid state UV laser etching may achieve etch resolutionsof less than 5-10 microns in FWNT films, as described above, in singlepasses even at power levels as low as 17 watts. Such etching may beperformed on a roll-to-roll apparatus, whereon a nanostructure film ismoving at a rate of more than 1-2 meters/second. Etching may be tuned byadjusting the laser power, pulse duration (e.g., milliseconds tofemtoseconds) and/or type (e.g., excimer, solid state, gas, chemical,fiber-hosted, semiconductor, dye and/or free electron) employed.High-power, short-pulse lasers may be desirable for improvingthroughput, while lower-power, long-pulse lasers may be desirable forimproving etch selectivity.

In another example, an inert gas dry etching process (e.g., reactive ionetching (RIE)) may be employed to etch carbon nanostructures. As usedherein, an “inert gas” refers to any gas, elemental or molecular, thatis not significantly reactive under normal circumstances (e.g., noblegases). Additionally, an “inert gas” shall include certain so-calledpseudo-inert gases, which are not usually considered inert but whichbehave like inert gases under given conditions (e.g., low pressureand/or plasma) and therefore can often be used inert gas substitutes indry etching processes. Inert gases have conventionally been used in dryetching processes only as dilutants rather than etchants, since they donot react significantly with most integrated-circuit (IC) materials.However, as employed in the present invention, such gases (e.g., Ar, He,Ne, Xe) can be employed as effective etch gases (e.g., for carbon), andare advantageous over many other dry etching processes (e.g., oxygen(O2) plasma) in that they can allow high selectivity control between,for example, carbon nanostructures (e.g., nanotubes) and protectionlayer materials such as silicon nitride (SiNx:H), silicon dioxide(SiO2), amorphous silicon (a-Si:) and poly-silicon (poly-Si). Moreover,the use of inert gas plasmas can avoid the undesirableetch-residue-induced contamination, halogen polymer residues, and/orcorrosion species caused by many fluorine (F) and chlorine (Cl) inducedplasma etching processes. Conventional dry etch gases (e.g., O2, F, Cl)may be used as well or instead. Additionally, etching with oxygen atatmospheric pressure and temperature has been effective in patterningnanostructure films, specifically those comprising carbon nanotubes.

In another exemplary embodiment, a nanostructure film may be patternedduring deposition, using a patterned stamp. Such a process may bescaled-up using, for example, micro-gravure printing, wherein themicro-gravure coater has a patterned surface.

Referring back to FIG. 2, the display arrangement 30 may be a standalone unit or it may integrated with other devices. When stand alone,the display arrangement 32 (or each of its components) acts like aperipheral device (monitor) that includes its own housing and that canbe coupled to a host device through wired or wireless connections. Whenintegrated, the display arrangement 30 shares a housing and is hardwired into the host device thereby forming a single unit. By way ofexample, the display arrangement 30 may be disposed inside a variety ofhost devices including but not limited to general purpose computers suchas a desktop, laptop or tablet computers, handhelds such as PDAs andmedia players such as music players, or peripheral devices such ascameras, printers and/or the like.

FIG. 4 is a multipoint touch method 45, in accordance with oneembodiment of the present invention. The method generally begins atblock 46 where multiple touches are received on the surface of thenanostructure-film touch screen at the same time. This may for examplebe accomplished by placing multiple fingers on the surface of thenanostructure-film touch screen. Following block 46, the process flowproceeds to block 47 where each of the multiple touches is separatelyrecognized by the nanostructure-film touch screen. This may for examplebe accomplished by multipoint capacitance sensors located within thenanostructure-film touch screen. Following block 47, the process flowproceeds to block 48 where the touch data based on multiple touches isreported. The touch data may for example be reported to a host devicesuch as a general purpose computer.

FIG. 5 is a block diagram of a computer system 50, in accordance withone embodiment of the present invention. The computer system 50 maycorrespond to personal computer systems such as desktops, laptops,tablets or handhelds. By way of example, the computer system maycorrespond to any Apple or PC based computer system. The computer systemmay also correspond to public computer systems such as informationkiosks, automated teller machines (ATM), point of sale machines (POS),industrial machines, gaming machines, arcade machines, vending machines,airline e-ticket terminals, restaurant reservation terminals, customerservice stations, library terminals, learning devices, and the like.

As shown, the computer system 50 includes a processor 56 configured toexecute instructions and to carry out operations associated with thecomputer system 50. For example, using instructions retrieved forexample from memory, the processor 56 may control the reception andmanipulation of input and output data between components of thecomputing system 50. The processor 56 can be a single-chip processor orcan be implemented with multiple components.

In most cases, the processor 56 together with an operating systemoperates to execute computer code and produce and use data. The computercode and data may reside within a program storage block 58 that isoperatively coupled to the processor 56. Program storage block 58generally provides a place to hold data that is being used by thecomputer system 50. By way of example, the program storage block mayinclude Read-Only Memory (ROM) 60, Random-Access Memory (RAM) 62, harddisk drive 64 and/or the like. The computer code and data could alsoreside on a removable storage medium and loaded or installed onto thecomputer system when needed. Removable storage mediums include, forexample, CD-ROM, PC-CARD, floppy disk, magnetic tape, and a networkcomponent.

The computer system 50 also includes an input/output (I/O) controller 66that is operatively coupled to the processor 56. The (I/O) controller 66may be integrated with the processor 56 or it may be a separatecomponent as shown. The I/O controller 66 is generally configured tocontrol interactions with one or more I/O devices. The I/O controller 66generally operates by exchanging data between the processor and the I/Odevices that desire to communicate with the processor. The I/O devicesand the I/O controller typically communicate through a data link 67. Thedata link 67 may be a one way link or two way link. In some cases, theI/O devices may be connected to the I/O controller 66 through wiredconnections. In other cases, the I/O devices may be connected to the I/Ocontroller 66 through wireless connections. By way of example, the datalink 67 may correspond to PS/2, USB, Firewire, IR, RF, Bluetooth or thelike.

The computer system 50 also includes a display device 68 that isoperatively coupled to the processor 56. The display device 68 may be aseparate component (peripheral device) or it may be integrated with theprocessor and program storage to form a desktop computer (all in onemachine), a laptop, handheld or tablet or the like. The display device68 is configured to display a graphical user interface (GUI) includingperhaps a pointer or cursor as well as other information to the user. Byway of example, the display device 68 may be a monochrome display, colorgraphics adapter (CGA) display, enhanced graphics adapter (EGA) display,variable-graphics-array (VGA) display, super VGA display, liquid crystaldisplay (e.g., active matrix, passive matrix and the like), cathode raytube (CRT), plasma displays and the like.

The computer system 50 also includes a nanostructure-film touch screen70 that is operatively coupled to the processor 56. Thenanostructure-film touch screen 70 is a transparent panel that ispositioned in front of the display device 68. The nanostructure-filmtouch screen 70 may be integrated with the display device 68 or it maybe a separate component. The nanostructure-film touch screen 70 isconfigured to receive input from a user's touch and to send thisinformation to the processor 56. In most cases, the nanostructure-filmtouch screen 70 recognizes touches and the position and magnitude oftouches on its surface. The nanostructure-film touch screen 70 reportsthe touches to the processor 56 and the processor 56 interprets thetouches in accordance with its programming. For example, the processor56 may initiate a task in accordance with a particular touch.

In accordance with one embodiment, the nanostructure-film touch screen70 is capable of tracking multiple objects, which rest on, tap on, ormove across the touch sensitive surface of the nanostructure-film touchscreen at the same time. The multiple objects may for example correspondto fingers and palms. Because the nanostructure-film touch screen iscapable of tracking multiple objects, a user may perform several touchinitiated tasks at the same time. For example, the user may select anonscreen button with one finger, while moving a cursor with anotherfinger. In addition, a user may move a scroll bar with one finger whileselecting an item from a menu with another finger. Furthermore, a firstobject may be dragged with one finger while a second object may bedragged with another finger. Moreover, gesturing may be performed withmore than one finger.

To elaborate, the nanostructure-film touch screen 70 generally includesa sensing device 72 configured to detect an object in close proximitythereto and/or the pressure exerted thereon. The sensing device 72 maybe widely varied. In one particular embodiment, the sensing device 72 isdivided into several independent and spatially distinct sensing points,nodes or regions 74 that are positioned throughout thenanostructure-film touch screen 70. The sensing points 74, which aretypically hidden from view, are dispersed about the nanostructure-filmtouch screen 70 with each sensing point 74 representing a differentposition on the surface of the nanostructure-film touch screen 70 (ortouch screen plane). The sensing points 74 may be positioned in a gridor a pixel array where each pixilated sensing point 74 is capable ofgenerating a signal at the same time. In the simplest case, a signal isproduced each time an object is positioned over a sensing point 74. Whenan object is placed over multiple sensing points 74 or when the objectis moved between or over multiple sensing point 74, multiple signals aregenerated.

The number and configuration of the sensing points 74 may be widelyvaried. The number of sensing points 74 generally depends on the desiredsensitivity as well as the desired transparency of thenanostructure-film nanostructure-film touch screen 70. More nodes orsensing points generally increases sensitivity, but reduces transparency(and vice versa). With regards to configuration, the sensing points 74generally map the touch screen plane into a coordinate system such as aCartesian coordinate system, a Polar coordinate system or some othercoordinate system. When a Cartesian coordinate system is used (asshown), the sensing points 74 typically correspond to x and ycoordinates. When a Polar coordinate system is used, the sensing pointstypically correspond to radial (r) and angular coordinates (.theta.).

The nanostructure-film touch screen 70 may include a sensing circuit 76that acquires the data from the sensing device 72 and that supplies theacquired data to the processor 56. Alternatively, the processor mayinclude this functionality. In one embodiment, the sensing circuit 76 isconfigured to send raw data to the processor 56 so that the processor 56processes the raw data. For example, the processor 56 receives data fromthe sensing circuit 76 and then determines how the data is to be usedwithin the computer system 50. The data may include the coordinates ofeach sensing point 74 as well as the pressure exerted on each sensingpoint 74. In another embodiment, the sensing circuit 76 is configured toprocess the raw data itself. That is, the sensing circuit 76 reads thepulses from the sensing points 74 and turns them into data that theprocessor 56 can understand. The sensing circuit 76 may performfiltering and/or conversion processes. Filtering processes are typicallyimplemented to reduce a busy data stream so that the processor 56 is notoverloaded with redundant or non-essential data. The conversionprocesses may be implemented to adjust the raw data before sending orreporting them to the processor 56. The conversions may includedetermining the center point for each touch region (e.g., centroid).

The sensing circuit 76 may include a storage element for storing a touchscreen program, which is a capable of controlling different aspects ofthe nanostructure-film touch screen 70. For example, the touch screenprogram may contain what type of value to output based on the sensingpoints 74 selected (e.g., coordinates). In fact, the sensing circuit inconjunction with the touch screen program may follow a predeterminedcommunication protocol. As is generally well known, communicationprotocols are a set of rules and procedures for exchanging data betweentwo devices. Communication protocols typically transmit information indata blocks or packets that contain the data to be transmitted, the datarequired to direct the packet to its destination, and the data thatcorrects errors that occur along the way. By way of example, the sensingcircuit may place the data in a HID format (Human Interface Device).

The sensing circuit 76 generally includes one or more microcontrollers,each of which monitors one or more sensing points 74. Themicrocontrollers may for example correspond to an application specificintegrated circuit (ASIC), which works with firmware to monitor thesignals from the sensing device 72 and to process the monitored signalsand to report this information to the processor 56.

In accordance with one embodiment, the sensing device 72 is based oncapacitance. As should be appreciated, whenever two electricallyconductive members come close to one another without actually touching,their electric fields interact to form capacitance. In most cases, thefirst electrically conductive member is a sensing point 74 and thesecond electrically conductive member is an object 80 such as a finger.As the object 80 approaches the surface of the nanostructure-film touchscreen 70, a tiny capacitance forms between the object 80 and thesensing points 74 in close proximity to the object 80. By detectingchanges in capacitance at each of the sensing points 74 and noting theposition of the sensing points, the sensing circuit can recognizemultiple objects, and determine the location, pressure, direction, speedand acceleration of the objects 80 as they are moved across thenanostructure-film touch screen 70. For example, the sensing circuit candetermine when and where each of the fingers and palm of one or morehands are touching as well as the pressure being exerted by the fingerand palm of the hand(s) at the same time.

The simplicity of capacitance allows for a great deal of flexibility indesign and construction of the sensing device 72. By way of example, thesensing device 72 may be based on self capacitance or mutualcapacitance. In self capacitance, each of the sensing points 74 isprovided by an individual charged electrode. As an object approaches thesurface of the nanostructure-film touch screen 70, the object capacitivecouples to those electrodes in close proximity to the object therebystealing charge away from the electrodes. The amount of charge in eachof the electrodes are measured by the sensing circuit 76 to determinethe positions of multiple objects when they touch the nanostructure-filmtouch screen 70. In mutual capacitance, the sensing device 72 includes atwo layer grid of spatially separated lines or wires. In the simplestcase, the upper layer includes lines in rows while the lower layerincludes lines in columns (e.g., orthogonal). The sensing points 74 areprovided at the intersections of the rows and columns. During operation,the rows are charged and the charge capacitively couples to the columnsat the intersection. As an object approaches the surface of thenanostructure-film touch screen, the object capacitive couples to therows at the intersections in close proximity to the object therebystealing charge away from the rows and therefore the columns as well.The amount of charge in each of the columns is measured by the sensingcircuit 76 to determine the positions of multiple objects when theytouch the nanostructure-film touch screen 70.

FIG. 6 is a partial top view of a transparent multiple pointnanostructure-film touch screen 100, in accordance with one embodimentof the present invention. By way of example, the nanostructure-filmtouch screen 100 may generally correspond to the nanostructure-filmtouch screen shown in FIGS. 2 and 4. The multipoint nanostructure-filmtouch screen 100 is capable of sensing the position and the pressure ofmultiple objects at the same time. This particular nanostructure-filmtouch screen 100 is based on self capacitance and thus it includes aplurality of transparent capacitive sensing electrodes 102, which eachrepresent different coordinates in the plane of the nanostructure-filmtouch screen 100. The electrodes 102 are configured to receivecapacitive input from one or more objects touching thenanostructure-film touch screen 100 in the vicinity of the electrodes102. When an object is proximate an electrode 102, the object stealscharge thereby affecting the capacitance at the electrode 102. Theelectrodes 102 are connected to a capacitive sensing circuit 104 throughtraces 106 that are positioned in the gaps 108 found between the spacedapart electrodes 102. The electrodes 102 are spaced apart in order toelectrically isolate them from each other as well as to provide a spacefor separately routing the sense traces 106. The gap 108 is preferablymade small so as to maximize the sensing area and to minimize opticaldifferences between the space and the transparent electrodes.

As shown, the sense traces 106 are routed from each electrode 102 to thesides of the nanostructure-film touch screen 100 where they areconnected to the capacitive sensing circuit 104. The capacitive sensingcircuit 104 includes one or more sensor ICs 110 that measure thecapacitance at each electrode 102 and that reports its findings or someform thereof to a host controller. The sensor ICs 110 may for exampleconvert the analog capacitive signals to digital data and thereaftertransmit the digital data over a serial bus to a host controller. Anynumber of sensor ICs may be used. For example, a single chip may be usedfor all electrodes, or multiple chips may be used for a single or groupof electrodes. In most cases, the sensor ICs 110 report trackingsignals, which are a function of both the position of the electrode 102and the intensity of the capacitance at the electrode 102.

The electrodes 102, traces 106 and sensing circuit 104 are generallydisposed on an optical transmissive member 112. In most cases, theoptically transmissive member 112 is formed from a clear material suchas glass or plastic. The electrode 102 and traces 106 may be placed onthe member 112 using any suitable patterning technique including forexample, deposition, etching, printing and the like. The electrodes 102and sense traces 106 comprise nanostructure films. By way of example,the electrodes 102 and traces 106 may be formed from random networks ofFWNTs. In addition, the sensor ICs 110 of the sensing circuit 104 can beelectrically coupled to the traces 106 using any suitable techniques. Inone implementation, the sensor ICs 110 are placed directly on the member112 (flip chip). In another implementation, a flex circuit is bonded tothe member 112, and the sensor ICs 110 are attached to the flex circuit.In yet another implementation, a flex circuit is bonded to the member112, a PCB is bonded to the flex circuit and the sensor ICs 110 areattached to the PCB. The sensor ICs may for example be capacitancesensing ICs.

The distribution of the electrodes 102 may be widely varied. Forexample, the electrodes 102 may be positioned almost anywhere in theplane of the nanostructure-film touch screen 100. The electrodes 102 maybe positioned randomly or in a particular pattern about the touch screen100. With regards to the later, the position of the electrodes 102 maydepend on the coordinate system used. For example, the electrodes 102may be placed in an array of rows and columns for Cartesian coordinatesor an array of concentric and radial segments for polar coordinates.Within each array, the rows, columns, concentric or radial segments maybe stacked uniformly relative to the others or they may be staggered oroffset relative to the others. Additionally, within each row or column,or within each concentric or radial segment, the electrodes 102 may bestaggered or offset relative to an adjacent electrode 102.

Furthermore, the electrodes 102 may be formed from almost any shapewhether simple (e.g., squares, circles, ovals, triangles, rectangles,polygons, and the like) or complex (e.g., random shapes). Further still,the shape of the electrodes 102 may have identical shapes or they mayhave different shapes. For example, one set of electrodes 102 may have afirst shape while a second set of electrodes 102 may have a second shapethat is different than the first shape. The shapes are generally chosento maximize the sensing area and to minimize optical differences betweenthe gaps and the transparent electrodes.

In addition, the size of the electrodes 102 may vary according to thespecific needs of each device. In some cases, the size of the electrodes102 corresponds to about the size of a finger tip. For example, the sizeof the electrodes 102 may be on the order of 4-5 mm2. In other cases,the size of the electrodes 102 are smaller than the size of the fingertip so as to improve resolution of the nanostructure-film touch screen100 (the finger can influence two or more electrodes at any one timethereby enabling interpolation). Like the shapes, the size of theelectrodes 102 may be identical or they may be different. For example,one set of electrodes 102 may be larger than another set of electrodes102. Moreover, any number of electrodes 102 may be used. The number ofelectrodes 102 is typically determined by the size of thenanostructure-film touch screen 100 as well as the size of eachelectrode 102. In most cases, it would be desirable to increase thenumber of electrodes 102 so as to provide higher resolution, i.e., moreinformation can be used for such things as acceleration.

Although the sense traces 106 can be routed a variety of ways, they aretypically routed in manner that reduces the distance they have to travelbetween their electrode 102 and the sensor circuit 104, and that reducesthe size of the gaps 108 found between adjacent electrodes 102. Thewidth of the sense traces 106 are also widely varied. The widths aregenerally determined by the amount of charge being distributed therethrough, the number of adjacent traces 106, and the size of the gap 108through which they travel. It is generally desirable to maximize thewidths of adjacent traces 106 in order to maximize the coverage insidethe gaps 108 thereby creating a more uniform optical appearance.

In the illustrated embodiment, the electrodes 102 are positioned in apixilated array. As shown, the electrodes 102 are positioned in rows 116that extend to and from the sides of the nanostructure-film touch screen100. Within each row 116, the identical electrodes 102 are spaced apartand positioned laterally relative to one another (e.g., juxtaposed).Furthermore, the rows 116 are stacked on top of each other therebyforming the pixilated array. The sense traces 106 are routed in the gaps108 formed between adjacent rows 106. The sense traces 106 for each roware routed in two different directions. The sense traces 106 on one sideof the row 116 are routed to a sensor IC 110 located on the left sideand the sense traces 106 on the other side of the row 116 are routed toanother sensor IC 110 located on the right side of thenanostructure-film touch screen 100. This is done to minimize the gap108 formed between rows 116. The gap 108 may for example be held toabout 20 microns. As should be appreciated, the spaces between thetraces can stack thereby creating a large gap between electrodes. Ifrouted to one side, the size of the space would be substantially doubledthereby reducing the resolution of the touch screen. Moreover, the shapeof the electrode 102 is in the form of a parallelogram, and moreparticularly a parallelogram with sloping sides.

FIG. 7 is a partial top view of a transparent multi pointnanostructure-film touch screen 120, in accordance with one embodimentof the present invention. In this embodiment, the nanostructure-filmtouch screen 120 is similar to the nanostructure-film touch screen 100shown in FIG. 6, however, unlike the nanostructure-film touch screen 100of FIG. 6, the nanostructure-film touch screen 120 shown in FIG. 7includes electrodes 122 with different sizes. As shown, the electrodes122 located in the center of the nanostructure-film touch screen 120 arelarger than the electrodes 122 located at the sides of thenanostructure-film touch screen 120. In fact, the height of theelectrodes 122 gets correspondingly smaller when moving from the centerto the edge of the nanostructure-film touch screen 120. This is done tomake room for the sense traces 124 extending from the sides of the morecentrally located electrodes 122. This arrangement advantageouslyreduces the gap found between adjacent rows 126 of electrodes 122.Although the height of each electrode 122 shrinks, the height H of therow 126 as well as the width W of each electrode 122 stays the same. Inone configuration, the height of the row 126 is substantially equal tothe width of each electrode 122. For example, the height of the row 126and the width of each electrode 122 may be about 4 mm to about 5 mm.

FIG. 8 is a front elevation view, in cross section of a displayarrangement 130, in accordance with one embodiment of the presentinvention. The display arrangement 130 includes an LCD display 132 and ananostructure-film touch screen 134 positioned over the LCD display 132.The nanostructure-film touch screen may for example correspond to thenanostructure-film touch screen shown in FIG. 6 or 7. The LCD display132 may correspond to any conventional LCD display known in the art.Although not shown, the LCD display 132 typically includes variouslayers including a fluorescent panel, polarizing filters, a layer ofliquid crystal cells, a color filter and the like.

The nanostructure-film touch screen 134 includes a transparent electrodelayer 136 that is positioned over a glass member 138. The glass member138 may be a portion of the LCD display 132 or it may be a portion ofthe nanostructure-film touch screen 134. In either case, the glassmember 138 is a relatively thick piece of clear glass that protects thedisplay 132 from forces, which are exerted on the nanostructure-filmtouch screen 134. The thickness of the glass member 138 may for examplebe about 2 mm. In most cases, the electrode layer 136 is disposed on theglass member 138 using the nanostructure-film deposition and patterningtechniques described above, such as slot-die coating and laser etching.Although not shown, in some cases, it may be necessary to coat theelectrode layer 136 with a material of similar refractive index toimprove the visual appearance of the touch screen. As should beappreciated, the gaps located between electrodes and traces do not havethe same optical index as the electrodes and traces, and therefore amaterial may be needed to provide a more similar optical index. By wayof example, index matching gels may be used.

The nanostructure-film touch screen 134 also includes a protective coversheet 140 disposed over the electrode layer 136. The electrode layer 136is therefore sandwiched between the glass member 138 and the protectivecover sheet 140. The protective sheet 140 serves to protect the underlayers and provide a surface for allowing an object to slide thereon.The protective sheet 140 also provides an insulating layer between theobject and the electrode layer 136. The protective cover sheet 140 maybe formed from any suitable clear material such as glass and plastic.The protective cover sheet 140 is suitably thin to allow for sufficientelectrode coupling. By way of example, the thickness of the cover sheet140 may be between about 0.3-0.8 mm. In addition, the protective coversheet 140 may be treated with coatings to reduce sticktion when touchingand reduce glare when viewing the underlying LCD display 132. By way ofexample, a low sticktion/anti reflective coating 142 may be applied overthe cover sheet 140. Although the electrode layer 136 is typicallypatterned on the glass member 138, it should be noted that in some casesit may be alternatively or additionally patterned on the protectivecover sheet 140.

FIG. 9 is a top view of a transparent multipoint nanostructure-filmtouch screen 150, in accordance with another embodiment of the presentinvention. By way of example, the nanostructure-film touch screen 150may generally correspond to the nanostructure-film touch screen of FIGS.2 and 4. Unlike the nanostructure-film touch screen shown in FIGS. 6-8,the nanostructure-film touch screen of FIG. 9 utilizes the concept ofmutual capacitance rather than self capacitance. As shown, thenanostructure-film touch screen 150 includes a two layer grid ofspatially separated lines or wires 152. In most cases, the lines 152 oneach layer are parallel one another. Furthermore, although in differentplanes, the lines 152 on the different layers are configured tointersect or cross in order to produce capacitive sensing nodes 154,which each represent different coordinates in the plane of thenanostructure-film touch screen 150. The nodes 154 are configured toreceive capacitive input from an object touching the nanostructure-filmtouch screen 150 in the vicinity of the node 154. When an object isproximate the node 154, the object steals charge thereby affecting thecapacitance at the node 154.

To elaborate, the lines 152 on different layers serve two differentfunctions. One set of lines 152A drives a current therethrough while thesecond set of lines 152B senses the capacitance coupling at each of thenodes 154. In most cases, the top layer provides the driving lines 152Awhile the bottom layer provides the sensing lines 152B. The drivinglines 152A are connected to a voltage source (not shown) that separatelydrives the current through each of the driving lines 152A. That is, thestimulus is only happening over one line while all the other lines aregrounded. They may be driven similarly to a raster scan. The sensinglines 152B are connected to a capacitive sensing circuit (not shown)that continuously senses all of the sensing lines 152B (always sensing).

When driven, the charge on the driving line 152A capacitively couples tothe intersecting sensing lines 152B through the nodes 154 and thecapacitive sensing circuit senses all of the sensing lines 152B inparallel. Thereafter, the next driving line 152A is driven, and thecharge on the next driving line 152A capacitively couples to theintersecting sensing lines 152B through the nodes 154 and the capacitivesensing circuit senses all of the sensing lines 152B in parallel. Thishappens sequential until all the lines 152A have been driven. Once allthe lines 152A have been driven, the sequence starts over (continuouslyrepeats). In most cases, the lines 152A are sequentially driven from oneside to the opposite side.

The capacitive sensing circuit typically includes one or more sensor ICsthat measure the capacitance in each of the sensing lines 152B and thatreports its findings to a host controller. The sensor ICs may forexample convert the analog capacitive signals to digital data andthereafter transmit the digital data over a serial bus to a hostcontroller. Any number of sensor ICs may be used. For example, a sensorIC may be used for all lines, or multiple sensor ICs may be used for asingle or group of lines. In most cases, the sensor ICs 110 reporttracking signals, which are a function of both the position of the node154 and the intensity of the capacitance at the node 154.

The lines 152 are generally disposed on one or more optical transmissivemembers 156 formed from a clear material such as glass or plastic. Byway of example, the lines 152 may be placed on opposing sides of thesame member 156 or they may be placed on different members 156. Thelines 152 may be placed on the member 156 using any suitable patterningtechnique including for example, deposition, etching, printing and thelike. The driving lines 152A are typically coupled to the voltage sourcethrough a flex circuit 158A, and the sensing lines 152B are typicallycoupled to the sensing circuit, and more particularly the sensor ICsthrough a flex circuit 158B. The sensor ICs may be attached to a printedcircuit board (PCB). Alternatively, the sensor ICs may be placeddirectly on the member 156 thereby eliminating the flex circuit 158B.

The distribution of the lines 152 may be widely varied. For example, thelines 152 may be positioned almost anywhere in the plane of thenanostructure-film touch screen 150. The lines 152 may be positionedrandomly or in a particular pattern about the nanostructure-film touchscreen 150. With regards to the later, the position of the lines 152 maydepend on the coordinate system used. For example, the lines 152 may beplaced in rows and columns for Cartesian coordinates or concentricallyand radially for polar coordinates. When using rows and columns, therows and columns may be placed at various angles relative to oneanother. For example, they may be vertical, horizontal or diagonal.

Furthermore, the lines 152 may be formed from almost any shape whetherrectilinear or curvilinear. The lines on each layer may be the same ordifferent. For example, the lines may alternate between rectilinear andcurvilinear. Further still, the shape of the opposing lines may haveidentical shapes or they may have different shapes. For example, thedriving lines may have a first shape while the sensing lines may have asecond shape that is different than the first shape. The geometry of thelines 152 (e.g., linewidths and spacing) may also be widely varied. Thegeometry of the lines within each layer may be identical or different,and further, the geometry of the lines for both layers may be identicalor different. By way of example, the linewidths of the sensing lines152B to driving lines 152A may have a ratio of about 2:1.

Moreover, any number of lines 152 may be used. It is generally believedthat the number of lines is dependent on the desired resolution of thenanostructure-film touch screen 150. The number of lines within eachlayer may be identical or different. The number of lines is typicallydetermined by the size of the nanostructure-film touch screen as well asthe desired pitch and linewidths of the lines 152.

In the illustrated embodiment, the driving lines 152A are positioned inrows and the sensing lines 152B are positioned in columns that areperpendicular to the rows. The rows extend horizontally to the sides ofthe nanostructure-film touch screen 150 and the columns extendvertically to the top and bottom of the nanostructure-film touch screen150. Furthermore, the linewidths for the set of lines 152A and 152B aredifferent and the pitch for set of lines 152A and 152B are equal to oneanother. In most cases, the linewidths of the sensing lines 152B arelarger than the linewidths of the driving lines 152A. By way of example,the pitch of the driving and sensing lines 152 may be about 5 mm, thelinewidths of the driving lines 152A may be about 1.05 mm and thelinewidths of the sensing lines 152B may be about 2.10 mm. Moreover, thenumber of lines 152 in each layer is different. For example, there maybe about 38 driving lines and about 50 sensing lines.

As mentioned above, the lines in order to form semi-transparentconductors on glass, film or plastic, may be a patterned nanostructurefilm. This is generally accomplished by depositing a nanostructure filmover the substrate surface and then etching away portions of thenanostructure film in order to form the lines. Additionally oralternatively, the pattern may be formed by a selective depositionmethod (e.g., stamping, inkjet printing, gravure coating). As should beappreciated, the areas with nanostructure film tend to have lowertransparency than the areas without nanostructure film. This isgenerally less desirable for the user as the user can distinguish thelines from the spaces therebetween, i.e., the patterned nanostructurefilm can become quite visible thereby producing a touch screen withundesirable optical properties.

In order to prevent the aforementioned problem, the dead areas betweenthe patterned nanostructure-film lines may be filled with indexingmatching materials. In another embodiment, rather than simply etchingaway all of the nanostructure film, the dead areas (the uncoveredspaces) may be subdivided into unconnected electrically floatingnanostructure-film pads, i.e., the dead areas may be patterned withspatially separated pads. The pads are typically separated with aminimum trace width. Furthermore, the pads are typically made small toreduce their impact on the capacitive measurements. This techniqueattempts to minimize the appearance of the lines by creating a uniformoptical retarder. That is, by seeking to create a uniform nanostructurefilm, it is believed that the panel will function closer to a uniformoptical retarder and therefore non-uniformities in the visual appearancewill be minimized. In yet another embodiment, a combination of indexmatching materials and unconnected floating pads may be used.

FIG. 10 is a partial front elevation view, in cross section of a displayarrangement 170, in accordance with one embodiment of the presentinvention. The display arrangement 170 includes an LCD display 172 and ananostructure-film touch screen 174 positioned over the LCD display 170.The nanostructure-film touch screen may for example correspond to thenanostructure-film touch screen shown in FIG. 9. The LCD display 172 maycorrespond to any conventional LCD display known in the art. Althoughnot shown, the LCD display 172 typically includes various layersincluding a fluorescent panel, polarizing filters, a layer of liquidcrystal cells, a color filter and the like.

The nanostructure-film touch screen 174 includes a transparent sensinglayer 176 that is positioned over a first glass member 178. The sensinglayer 176 includes a plurality of sensor lines 177 positioned in columns(extend in and out of the page). The first glass member 178 may be aportion of the LCD display 172 or it may be a portion of thenanostructure-film touch screen 174. For example, it may be the frontglass of the LCD display 172 or it may be the bottom glass of thenanostructure-film touch screen 174. The sensor layer 176 is typicallydisposed on the glass member 178 using suitable transparent conductivematerials and patterning techniques. In some cases, it may be necessaryto coat the sensor layer 176 with material of similar refractive indexto improve the visual appearance, i.e., make more uniform.

The nanostructure-film touch screen 174 also includes a transparentdriving layer 180 that is positioned over a second glass member 182. Thesecond glass member 182 is positioned over the first glass member 178.The sensing layer 176 is therefore sandwiched between the first andsecond glass members 178 and 182. The second glass member 182 providesan insulating layer between the driving and sensing layers 176 and 180.The driving layer 180 includes a plurality of driving lines 181positioned in rows (extend to the right and left of the page). Thedriving lines 181 are configured to intersect or cross the sensing lines177 positioned in columns in order to form a plurality of capacitivecoupling nodes 182. Like the sensing layer 176, the driving layer 180 isdisposed on the glass member using suitable materials and patterningtechniques. Furthermore, in some cases, it may be necessary to coat thedriving layer 180 with material of similar refractive index to improvethe visual appearance. Although the sensing layer is typically patternedon the first glass member, it should be noted that in some cases it maybe alternatively or additionally patterned on the second glass member.

The nanostructure-film touch screen 174 also includes a protective coversheet 190 disposed over the driving layer 180. The driving layer 180 istherefore sandwiched between the second glass member 182 and theprotective cover sheet 190. The protective cover sheet 190 serves toprotect the under layers and provide a surface for allowing an object toslide thereon. The protective cover sheet 190 also provides aninsulating layer between the object and the driving layer 180. Theprotective cover sheet is suitably thin to allow for sufficientcoupling. The protective cover sheet 190 may be formed from any suitableclear material such as glass and plastic. In addition, the protectivecover sheet 190 may be treated with coatings to reduce sticktion whentouching and reduce glare when viewing the underlying LCD display 172.By way of example, a low sticktion/anti reflective coating may beapplied over the cover sheet 190. Although the line layer is typicallypatterned on a glass member, it should be noted that in some cases itmay be alternatively or additionally patterned on the protective coversheet.

The nanostructure-film touch screen 174 also includes various bondinglayers 192. The bonding layers 192 bond the glass members 178 and 182 aswell as the protective cover sheet 190 together to form the laminatedstructure and to provide rigidity and stiffness to the laminatedstructure. In essence, the bonding layers 192 help to produce amonolithic sheet that is stronger than each of the individual layerstaken alone. In most cases, the first and second glass members 178 and182 as well as the second glass member and the protective sheet 182 and190 are laminated together using a bonding agent such as glue. Thecompliant nature of the glue may be used to absorb geometric variationsso as to form a singular composite structure with an overall geometrythat is desirable. In some cases, the bonding agent includes an indexmatching material to improve the visual appearance of thenanostructure-film touch screen 170.

With regards to configuration, each of the various layers may be formedwith various sizes, shapes, and the like. For example, each of thelayers may have the same thickness or a different thickness than theother layers in the structure. In the illustrated embodiment, the firstglass member 178 has a thickness of about 1.1 mm, the second glassmember 182 has a thickness of about 0.4 mm and the protective sheet hasa thickness of about 0.55 mm. The thickness of the bonding layers 192typically varies in order to produce a laminated structure with adesired height. Furthermore, each of the layers may be formed withvarious materials. By way of example, each particular type of layer maybe formed from the same or different material. For example, any suitableglass or plastic material may be used for the glass members. In asimilar manner, any suitable bonding agent may be used for the bondinglayers 192.

FIGS. 11A and 11B are partial top view diagrams of a driving layer 200and a sensing layer 202, in accordance with one embodiment. In thisembodiment, each of the layers 200 and 202 includes dummy features 204disposed between the driving lines 206 and the sensing lines 208. Thedummy features 204 are configured to optically improve the visualappearance of the nanostructure-film touch screen by more closelymatching the optical index of the lines. While index matching materialsmay improve the visual appearance, it has been found that there stillmay exist some non-uniformities. The dummy features 204 provide thenanostructure-film touch screen with a more uniform appearance. Thedummy features 204 are electrically isolated and positioned in the gapsbetween each of the lines 206 and 208. Although they may be patternedseparately, the dummy features 204 are typically patterned along withthe lines 206 and 208. Furthermore, although they may be formed fromdifferent materials, the dummy features 204 are typically formed withnanostructure film to provide the best possible index matching. Asshould be appreciated, the dummy features will more than likely stillproduce some gaps, but these gaps are much smaller than the gaps foundbetween the lines (many orders of magnitude smaller). These gaps,therefore have minimal impact on the visual appearance. While this maybe the case, index matching materials may be additionally applied to thegaps between the dummy features to further improve the visual appearanceof the nanostructure-film touch screen. The distribution, size, number,dimension, and shape of the dummy features may be widely varied.

FIG. 12 is a simplified diagram of a mutual capacitance circuit 220, inaccordance with one embodiment of the present invention. The mutualcapacitance circuit 220 includes a driving line 222 and a sensing line224 that are spatially separated thereby forming a capacitive couplingnode 226. The driving line 222 is electrically coupled to a voltagesource 228, and the sensing line 224 is electrically coupled to acapacitive sensing circuit 230. The driving line 222 is configured tocarry a current to the capacitive coupling node 226, and the sensingline 224 is configured to carry a current to the capacitive sensingcircuit 230. When no object is present, the capacitive coupling at thenode 226 stays fairly constant. When an object 232 such as a finger isplaced proximate the node 226, the capacitive coupling changes throughthe node 226 changes. The object 232 effectively shunts some of thefield away so that the charge projected across the node 226 is less. Thechange in capacitive coupling changes the current that is carried by thesensing lines 224. The capacitive sensing circuit 230 notes the currentchange and the position of the node 226 where the current changeoccurred and reports this information in a raw or in some processed formto a host controller. The capacitive sensing circuit does this for eachnode 226 at about the same time (as viewed by a user) so as to providemultipoint sensing.

The sensing line 224 may contain a filter 236 for eliminating parasiticcapacitance 237, which may for example be created by the large surfacearea of the row and column lines relative to the other lines and thesystem enclosure at ground potential. Generally speaking, the filterrejects stray capacitance effects so that a clean representation of thecharge transferred across the node 226 is outputted (and not anything inaddition to that). That is, the filter 236 produces an output that isnot dependent on the parasitic capacitance, but rather on thecapacitance at the node 226. As a result, a more accurate output isproduced.

FIG. 13 is a diagram of an inverting amplifier 240, in accordance withone embodiment of the present invention. The inverting amplifier 240 maygenerally correspond to the filter 236 shown in FIG. 12. As shown, theinverting amplifier includes a non inverting input that is held at aconstant voltage (in this case ground), an inverting input that iscoupled to the node and an output that is coupled to the capcitivesensing circuit 230. The output is coupled back to the inverting inputthrough a capacitor. During operation, the input from the node may bedisturbed by stray capacitance effects, i.e., parasitic capacitance. Ifso, the inverting amplifier is configured to drive the input back to thesame voltage that it had been previously before the stimulus. As such,the value of the parasitic capacitance doesn't matter.

FIG. 14 is a block diagram of a capacitive sensing circuit 260, inaccordance with one embodiment of the present invention. The capacitivesensing circuit 260 may for example correspond to the capacitive sensingcircuits described in the previous figures. The capacitive sensingcircuit 260 is configured to receive input data from a plurality ofsensing points 262 (electrode, nodes, etc.), to process the data and tooutput processed data to a host controller.

The sensing circuit 260 includes a multiplexer 264 (MUX). Themultiplexer 264 is a switch configured to perform time multiplexing. Asshown, the MUX 264 includes a plurality of independent input channels266 for receiving signals from each of the sensing points 262 at thesame time. The MUX 264 stores all of the incoming signals at the sametime, but sequentially releases them one at a time through an outputchannel 268.

The sensing circuit 260 also includes an analog to digital converter 270(ADC) operatively coupled to the MUX 264 through the output channel 268.The ADC 270 is configured to digitize the incoming analog signalssequentially one at a time. That is, the ADC 270 converts each of theincoming analog signals into outgoing digital signals. The input to theADC 270 generally corresponds to a voltage having a theoreticallyinfinite number of values. The voltage varies according to the amount ofcapacitive coupling at each of the sensing points 262. The output to theADC 270, on the other hand, has a defined number of states. The statesgenerally have predictable exact voltages or currents.

The sensing circuit 260 also includes a digital signal processor 272(DSP) operatively coupled to the ADC 270 through another channel 274.The DSP 272 is a programmable computer processing unit that works toclarify or standardize the digital signals via high speed mathematicalprocessing. The DSP 274 is capable of differentiating between human madesignals, which have order, and noise, which is inherently chaotic. Inmost cases, the DSP performs filtering and conversion algorithms usingthe raw data. By way of example, the DSP may filter noise events fromthe raw data, calculate the touch boundaries for each touch that occurson the touch screen at the same time, and thereafter determine thecoordinates for each touch event. The coordinates of the touch eventsmay then be reported to a host controller where they can be compared toprevious coordinates of the touch events to determine what action toperform in the host device.

FIG. 15 is a flow diagram 280, in accordance with one embodiment of thepresent invention. The method generally begins at block 282 where aplurality of sensing points are driven. For example, a voltage isapplied to the electrodes in self capacitance touch screens or throughdriving lines in mutual capacitance touch screens. In the later, eachdriving line is driven separately. That is, the driving lines are drivenone at a time thereby building up charge on all the intersecting sensinglines. Following block 282, the process flow proceeds to block 284 wherethe outputs (voltage) from all the sensing points are read. This blockmay include multiplexing and digitizing the outputs. For example, inmutual capacitance touch screens, all the sensing points on one row aremultiplexed and digitized and this is repeated until all the rows havebeen sampled. Following block 284, the process flow proceeds to block286 where an image or other form of data (signal or signals) of thetouch screen plane at one moment in time can be produced and thereafteranalyzed to determine where the objects are touching the touch screen.By way of example, the boundaries for each unique touch can becalculated, and thereafter the coordinates thereof can be found.Following block 286, the process flow proceeds to block 288 where thecurrent image or signal is compared to a past image or signal in orderto determine a change in pressure, location, direction, speed andacceleration for each object on the plane of the touch screen. Thisinformation can be subsequently used to perform an action as for examplemoving a pointer or cursor or making a selection as indicated in block290.

FIG. 16 is a flow diagram of a digital signal processing method 300, inaccordance with one embodiment of the present invention. By way ofexample, the method may generally correspond to block 286 shown anddescribed in FIG. 15. The method 300 generally begins at block 302 wherethe raw data is received. The raw data is typically in a digitized form,and includes values for each node of the touch screen. The values may bebetween 0 and 256 where 0 equates to the highest capacitive coupling (notouch pressure) and 256 equates to the least capacitive coupling (fulltouch pressure). An example of raw data at one point in time is shown inFIG. 17A. As shown in FIG. 17A, the values for each point are providedin gray scale where points with the least capacitive coupling are shownin white and the points with the highest capacitive coupling are shownin black and the points found between the least and the highestcapacitive coupling are shown in gray.

Following block 302, the process flow proceeds to block 304 where theraw data is filtered. As should be appreciated, the raw data typicallyincludes some noise. The filtering process is configured to reduce thenoise. By way of example, a noise algorithm may be run that removespoints that aren't connected to other points. Single or unconnectedpoints generally indicate noise while multiple connected pointsgenerally indicate one or more touch regions, which are regions of thetouch screen that are touched by objects. An example of a filtered datais shown in FIG. 17B. As shown, the single scattered points have beenremoved thereby leaving several concentrated areas.

Following block 304, the process flow proceeds to block 306 wheregradient data is generated. The gradient data indicates the topology ofeach group of connected points. The topology is typically based on thecapacitive values for each point. Points with the lowest values aresteep while points with the highest values are shallow. As should beappreciated, steep points indicate touch points that occurred withgreater pressure while shallow points indicate touch points thatoccurred with lower pressure. An example of gradient data is shown inFIG. 17C.

Following block 306, the process flow proceeds to block 308 where theboundaries for touch regions are calculated based on the gradient data.In general, a determination is made as to which points are groupedtogether to form each touch region. An example of the touch regions isshown in FIG. 17D.

In one embodiment, the boundaries are determined using a watershedalgorithm. Generally speaking, the algorithm performs imagesegmentation, which is the partitioning of an image into distinctregions as for example the touch regions of multiple objects in contactwith the touch screen. The concept of watershed initially comes from thearea of geography and more particularly topography where a drop of waterfalling on a relief follows a descending path and eventually reaches aminimum, and where the watersheds are the divide lines of the domains ofattracting drops of water. Herein, the watershed lines represent thelocation of pixels, which best separate different objects touching thetouch screen. Watershed algorithms can be widely varied. In oneparticular implementation, the watershed algorithm includes formingpaths from low points to a peak (based on the magnitude of each point),classifying the peak as an ID label for a particular touch region,associating each point (pixel) on the path with the peak. These stepsare performed over the entire image map thus carving out the touchregions associated with each object in contact with the touch screen.

Following block 308, the process flow proceeds to block 310 where thecoordinates for each of the touch regions are calculated. This may beaccomplished by performing a centroid calculation with the raw dataassociated with each touch region. For example, once the touch regionsare determined, the raw data associated therewith may be used tocalculate the centroid of the touch region. The centroid may indicatethe central coordinate of the touch region. By way of example, the X andY centroids may be found using the following equations:Xc=.SIGMA.Z*x/.SIGMA.Z; and Yc=.SIGMA.Z*y/.SIGMA.Z, where Xc representsthe x centroid of the touch region Yc represents the y centroid of thetouch region x represents the x coordinate of each pixel or point in thetouch region y represents the y coordinate of each pixel or point in thetouch region Z represents the magnitude (capacitance value) at eachpixel or point.

An example of a centroid calculation for the touch regions is shown inFIG. 17E. As shown, each touch region represents a distinct x and ycoordinate. These coordinates may be used to perform multipoint trackingas indicated in block 312. For example, the coordinates for each of thetouch regions may be compared with previous coordinates of the touchregions to determine positioning changes of the objects touching thetouch screen or whether or not touching objects have been added orsubtracted or whether a particular object is being tapped.

FIGS. 18 and 19 are side elevation views of an electronic device 350, inaccordance with multiple embodiments of the present invention. Theelectronic device 350 includes an LCD display 352 and a transparentnanostructure-film touch screen 354 positioned over the LCD display 352.The nanostructure-film touch screen 354 includes a protective sheet 356,one or more sensing layers 358, and a bottom glass member 360. In thisembodiment, the bottom glass member 360 is the front glass of the LCDdisplay 352. Further, the sensing layers 358 may be configured foreither self or mutual capacitance as described above. The sensing layers358 generally include a plurality of interconnects at the edge of thenanostructure-film touch screen for coupling the sensing layer 358 to asensing circuit (not shown). By way of example, the sensing layer 358may be electrically coupled to the sensing circuit through one or moreflex circuits 362, which are attached to the sides of thenanostructure-film touch screen 354.

As shown, the LCD display 352 and nanostructure-film touch screen 354are disposed within a housing 364. The housing 364 serves to cover andsupport these components in their assembled position within theelectronic device 350. The housing 364 provides a space for placing theLCD display 352 and nanostructure-film touch screen 354 as well as anopening 366 so that the display screen can be seen through the housing364. In one embodiment, as shown in FIG. 18, the housing 364 includes afacade 370 for covering the sides the LCD display 352 andnanostructure-film touch screen 354. Although not shown in great detail,the facade 370 is positioned around the entire perimeter of the LCDdisplay 352 and nanostructure-film touch screen 354. The facade 370serves to hide the interconnects leaving only the active area of the LCDdisplay 352 and nanostructure-film touch screen 354 in view.

In another embodiment, as shown in FIG. 19, the housing 364 does notinclude a facade 370, but rather a mask 372 that is printed on interiorportion of the top glass 374 of the nanostructure-film touch screen 354that extends between the sides of the housing 364. This particulararrangement makes the mask 372 look submerged in the top glass 356. Themask 372 serves the same function as the facade 370, but is a moreelegant solution. In one implementation, the mask 372 is a formed fromhigh temperature black polymer. In the illustrated embodiment of FIG.19, the nanostructure-film touch screen 354 is based on mutualcapacitance sensing and thus the sensing layer 358 includes drivinglines 376 and sensing lines 378. The driving lines 376 are disposed onthe top glass 356 and the mask 372, and the sensing lines 378 aredisposed on the bottom glass 360. The driving lines and sensing lines376 and 378 are insulated from one another via a spacer 380. The spacer380 may for example be a clear piece of plastic with optical matchingmaterials retained therein or applied thereto.

In one embodiment and referring to both FIGS. 18 and 19, the electronicdevice 350 corresponds to a tablet computer. In this embodiment, thehousing 364 also encloses various integrated circuit chips and othercircuitry 382 that provide computing operations for the tablet computer.By way of example, the integrated circuit chips and other circuitry mayinclude a microprocessor, motherboard, Read-Only Memory (ROM),Random-Access Memory (RAM), a hard drive, a disk drive, a battery, andvarious input/output support devices.

FIG. 20 is a partial front elevation view, in cross section of a displayarrangement 270, in accordance with another embodiment of the presentinvention. The display arrangement 270 includes an LCD display 172 and ananostructure-film touch screen 274 positioned over the LCD display 170.The nanostructure-film touch screen may for example correspond to thenanostructure-film touch screen shown in FIG. 9. The LCD display 172 maycorrespond to any conventional LCD display known in the art. Althoughnot shown, the LCD display 172 typically includes various layersincluding a fluorescent panel, polarizing filters, a layer of liquidcrystal cells, a color filter and the like.

The nanostructure-film touch screen 274 includes a transparent sensinglayer 176 that is positioned over a substrate 278. The sensing layer 176includes a plurality of sensor lines 177 positioned in columns (extendin and out of the page). The substrate 278 may comprise glass, as inprevious examples, and/or other transparent materials such aspolyethylene terephthalate (PET), polyethylene naphthalate (PEN),polycarbonate (PC), polyethersulfone (PES) and/or Arton. Flexiblesubstrates may be advantageous in that they are compatible withroll-to-roll processing (e.g., nanostructure film coating and/orpatterning). As compared to a batch process, which handles only onecomponent at a time, a roll-to-roll process represents a dramaticdeviation from current manufacturing practices, and can reduce capitalequipment and device part costs, while significantly increasingthroughput.

In addition to sensor layer 176, shielding layer 279 may be coated ontosubstrate 278 (e.g., a common substrate). Shielding layer 279 may beoptically transparent and electrically conductive, so as to at leastpartially shield touch screen 274 from electric field(s) emanating fromLCD 172. Both sensor layer 176 and shielding layer 279 may comprisenanostructure films. These layers may be coated onto substrate 278separately and/or simultaneously (e.g., by dip-coating).

The nanostructure-film touch screen 274 also includes a transparentdriving layer 180. This layer may be positioned over a dielectric layer282 deposited over sensor layer 176. The sensing layer 176 is thereforesandwiched between the substrate 278 and dielectric layer 282.Dielectric layer 282 provides an insulating layer between the drivingand sensing layers 176 and 180, and may comprise, for example, an epoxyor heat/UV-curable polymer such as poly(4-vinyl phenol). As in previousembodiments, the driving layer 180 includes a plurality of driving lines181 positioned in rows (extend to the right and left of the page). Thedriving lines 181 are configured to intersect or cross the sensing lines177 positioned in columns in order to form a plurality of capacitivecoupling nodes 182. Like the sensing layer 176, the driving layer 180may comprise a nanostructure film, and may be coated using suitablematerials and patterning techniques.

The nanostructure-film touch screen 174 may also include a protectivecover sheet 190 disposed over the driving layer 180. The driving layer180 is therefore sandwiched between dielectric layer 282 and theprotective cover sheet 190. The protective cover sheet 190 serves toprotect the under layers and provide a surface for allowing an object toslide thereon. The protective cover sheet 190 also provides aninsulating layer between the object and the driving layer 180. Theprotective cover sheet is suitably thin to allow for sufficientcoupling. The protective cover sheet 190 may be formed from any suitableclear material such as glass and plastic. In addition, the protectivecover sheet 190 may be treated with coatings to reduce sticktion whentouching and reduce glare when viewing the underlying LCD display 172.By way of example, a low sticktion/anti reflective coating may beapplied over the cover sheet 190. Although the line layer is typicallypatterned on a glass member, it should be noted that in some cases itmay be alternatively or additionally patterned on the protective coversheet.

Protective cover sheet 190 may be attached to touch screen 274 bybonding layer 192. The bonding layers 192, substrate 278 and protectivecover sheet 190 may together form a laminated structure havingsubstantial rigidity and stiffness.

With regards to configuration, each of the various layers may be formedwith various sizes, shapes, and the like.

In one exemplary embodiment, sensing and shielding layers may be coatedand patterned on opposite sides of a common substrate, while a depositedinsulating layer (e.g., epoxy and/or heat/UV-curable polymer) separatesthe sensing layer and the driving layer. For example, a common substratemay be dip-coated in a nanotube dispersion, such that transparent,conductive nanotube films (e.g., as described above) are formed on bothsides of the common substrate. The film on one side of the substrate maybe patterned to form a sensing layer, over which an electricallyinsulating material (e.g., a polymer) may be deposited to form adielectric layer, while the film on the other side of the substrate mayremain unpatterned to form a shielding layer. Another transparent,conductive nanotube film may then be formed on the dielectric layer(e.g., by a solution-based deposition, as described above), andpatterned to form a driving layer. A protective cover sheet may beplaced over the driving layer, e.g., attached via a bonding layer.

In one exemplary embodiment, sensing and driving layers may be coatedand patterned on opposite sides of a common substrate, while a depositedinsulating layer (e.g., epoxy and/or heat/UV-curable polymer) separatesthe sensing layer and the shielding layer. For example, a commonsubstrate may be dip-coated in a nanotube dispersion, such thattransparent, conductive nanotube films (e.g., as described above) areformed on both sides of the common substrate. The film on one side ofthe substrate may be patterned to form a sensing layer, over which anelectrically insulating material (e.g., a polymer) may be deposited toform a first dielectric layer. Another transparent, conductive nanotubefilm may then be formed on the first dielectric layer (e.g., by asolution-based deposition, as described above), to form a shieldinglayer. The film on the other side of the substrate may be patterned toform a driving layer, over which a protective cover sheet may be placed,e.g., attached via a bonding layer.

In one exemplary embodiment, sensing and driving layers may be coatedand patterned on the same side of a common substrate, and separated by adeposited insulating layer. For example, a transparent, conductivenanotube film may be deposited on one side of a common substrate (e.g.,a protective cover sheet), and patterned to form a driving layer. Anelectrically insulating material (e.g., a polymer) may be deposited overthis driving layer to form a dielectric layer. A second transparent,conductive nanotube film may be deposited over the dielectric layer, andpatterned to form a sensing layer. An electrically insulating materialmay be deposited over this sensing layer to form a second dielectriclayer, on which a third transparent, conductive nanotube film may bedeposited to form a shielding layer.

While the driving layer, sensing layer and shielding layer may allcomprise transparent, conductive nanotube films, such layers need nothave the same optoelectronic properties. For example, it may beadvantageous to make the shielding layer thinner than the driving layerand/or the sensing layer, such that the shielding layer has a higheroptical transparency but a lower electrical conductivity than thedriving layer and/or the sensing layer. Likewise, it may be advantageousto pattern certain layers (e.g., the driving layer and/or sensinglayer), and not others (e.g., the shielding layer).

The present invention has been described above with reference topreferred features and embodiments. Those skilled in the art willrecognize, however, that changes and modifications may be made in thesepreferred embodiments without departing from the scope of the presentinvention.

What is claimed is:
 1. A touch screen, comprising: a sensing layer; adriving layer; a substrate, and a shielding layer configured to shieldthe touch screen from an electric field, wherein the touch screen candetect multiple touches or near touches that occur at the same time andat distinct locations in a plane of the touch screen and producedistinct signals representative of the location of the touches on theplane of the touch screen for each of the multiple touches, wherein atleast one of the sensing layer and the driving layer comprises a firstnanostructure film, wherein the first nanostructure film is opticallytransparent and electrically conductive, wherein the sensing layer andthe driving layer are separated by a first insulating layer, and whereinthe sensing layer and the shielding layer are positioned on oppositesides of the substrate, wherein the shielding layer comprises a secondnanostructure film, and wherein the second nanostructure film isoptically transparent and electrically conductive.
 2. The touch screenof claim 1, wherein the sensing layer and the driving layer are formedon the substrate.
 3. The touch screen of claim 2, wherein the first andsecond nanostructure films each comprise at least one interconnectednetwork of nanotubes.
 4. The touch screen of claim 3, wherein the firstand second nanostructure films are formed on opposite sides of thesubstrate.
 5. The touch screen of claim 1, wherein the firstnanostructure film comprises at least one interconnected network ofnanotubes.
 6. The touch screen of claim 1, further comprising: a LCDcoupled to the shielding layer, wherein the LCD and the sensing layerare separated by the shielding layer and the substrate.
 7. The touchscreen of claim 1, wherein the sensing layer is on the substrate, thefirst insulating layer is on the sensing layer, and the driving layer ison the first insulating layer.
 8. A method of forming a touch screen,comprising: depositing a sensing layer and a driving layer on a firstside of a substrate; and depositing a shielding layer on a second sideof the substrate, wherein the shielding layer and the sensing layer aredeposited on opposite sides of the substrate simultaneously, wherein thetouch screen can detect multiple touches or near touches that occur atthe same time and at distinct locations in the plane of the touch screenand produce distinct signals representative of the location of thetouches on the plane of the touch screen for each of the multipletouches, wherein the shielding layer comprises a nanostructure film, andwherein the nanostructure film is optically transparent and electricallyconductive.
 9. The method of claim 8, further comprising: depositing aninsulating layer over at least one of the sensing layer, the drivinglayer and the shielding layer.
 10. The method of claim 9, wherein theinsulating layer and the nanostructure film are deposited usingsolution-based deposition methods.
 11. The method of claim 10, whereinat least two of the sensing layer, the driving layer and the shieldinglayer comprise nanostructure films.
 12. A method of forming a touchscreen, comprising: forming a sensing layer and a shielding layer onopposite sides of a substrate, the shielding layer being configured toshield the touch screen from an electric field, wherein the touch screencan detect multiple touches or near touches that occur at the same timeand at distinct locations in a plane of the touch screen and producedistinct signals representative of the location of the touches on theplane of the touch screen for each of the multiple touches; forming aninsulating layer on the sensing layer; forming a driving layer on theinsulating layer, wherein at least one of the sensing layer and thedriving layer include a first nanostructure film, the firstnanostructure film is optically transparent and electrically conductive,the shielding layer comprises a second nanostructure film, and thesecond nanostructure film is optically transparent and electricallyconductive.
 13. The method of claim 12, wherein the first and secondnanostructure films each comprises at least one interconnected networkof nanotubes.
 14. The method of claim 12, further comprising: coupling aLCD to the shielding layer, wherein the LCD and the sensing layer areseparated by the shielding layer and the substrate.